Helmet fin



FIG. 1 is a left-side view of a helmet fin showing my design;

FIG. 2 is a right-side view thereof;

FIG. 3 is a top view thereof, the bottom being unornamented;

FIG. 4 is a front view thereof;

FIG. 5 is a rear view thereof;

FIG. 6 is a perspective view thereof;

FIG. 7 is a perspective view of a helmet fin showing my design in a usage environment;

FIG. 8 is a top view thereof;

FIG. 9 is a rear view thereof; and,

FIG. 10 is a right view thereof.

The broken lines in FIGS. 7-10 depict environmental subject matter that forms no part of the claimed design. 

CLAIM I claim the ornamental design for a helmet fin, as shown and described. 